There is a need to determine the relative positions of certain objects in optical imaging systems. For example, the positions of focusing and zoom lenses or lens systems have to be accurately adjusted.
U.S. Pat. Nos. 5,587,846 and 5,430,375 disclose position-detecting systems using magneto-resistors and magnetic field generating elements.
The resistance value of a magneto-resistor depends on the magnetic field. Thus the movement of the magnetic field generating elements with respect to the magneto-resistors cause variations of the resistance values of the magneto-resistors. According to the patents U.S. Pat. Nos. 5,587,846 and 5,430,375, the magneto-resistors are arranged in pairs, each pair being connected in series thus that a predetermined voltage difference is applied over each pair. The common connection point of the two resistors of each pair generates a voltage signal, which depends on the resistance values of the resistors. Consequently, the generated voltage depends on the relative position of the magnetic field generating elements. The generated voltage signals are subsequently processed and analyzed to obtain the information regarding the relative position of said movable object.